Revert "drm/qxl: simplify qxl_fence_wait"

This reverts commit 5a838e5d.

Changes from commit 5a838e5d ("drm/qxl: simplify qxl_fence_wait") would
result in a '[TTM] Buffer eviction failed' exception whenever it reached a
timeout.
Due to a dependency to DMA_FENCE_WARN this also restores some code deleted
by commit d72277b6 ("dma-buf: nuke DMA_FENCE_TRACE macros v2").

Fixes: 5a838e5d ("drm/qxl: simplify qxl_fence_wait")
Link: https://lore.kernel.org/regressions/ZTgydqRlK6WX_b29@eldamar.lan/Reported-by: Timo Lindfors <timo.lindfors@iki.fi>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1054514Signed-off-by: Alex Constantino <dreaming.about.electric.sheep@gmail.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404181448.1643-2-dreaming.about.electric.sheep@gmail.com

drivers/gpu/drm/qxl/qxl_release.c

@@ -58,16 +58,56 @@ static long qxl_fence_wait(struct dma_fence *fence, bool intr,
 			   signed long timeout)
 {
 	struct qxl_device *qdev;
+	struct qxl_release *release;
+	int count = 0, sc = 0;
+	bool have_drawable_releases;
 	unsigned long cur, end = jiffies + timeout;
 
 	qdev = container_of(fence->lock, struct qxl_device, release_lock);
+	release = container_of(fence, struct qxl_release, base);
+	have_drawable_releases = release->type == QXL_RELEASE_DRAWABLE;
+
+retry:
+	sc++;
+
+	if (dma_fence_is_signaled(fence))
+		goto signaled;
+
+	qxl_io_notify_oom(qdev);
+
+	for (count = 0; count < 11; count++) {
+		if (!qxl_queue_garbage_collect(qdev, true))
+			break;
+
+		if (dma_fence_is_signaled(fence))
+			goto signaled;
+	}
 
-	if (!wait_event_timeout(qdev->release_event,
-				(dma_fence_is_signaled(fence) ||
-				 (qxl_io_notify_oom(qdev), 0)),
-				timeout))
+	if (dma_fence_is_signaled(fence))
+		goto signaled;
+
+	if (have_drawable_releases || sc < 4) {
+		if (sc > 2)
+			/* back off */
+			usleep_range(500, 1000);
+
+		if (time_after(jiffies, end))
 			return 0;
 
+		if (have_drawable_releases && sc > 300) {
+			DMA_FENCE_WARN(fence,
+				       "failed to wait on release %llu after spincount %d\n",
+				       fence->context & ~0xf0000000, sc);
+			goto signaled;
+		}
+		goto retry;
+	}
+	/*
+	 * yeah, original sync_obj_wait gave up after 3 spins when
+	 * have_drawable_releases is not set.
+	 */
+
+signaled:
 	cur = jiffies;
 	if (time_after(cur, end))
 		return 0;

include/linux/dma-fence.h

@@ -682,4 +682,11 @@ static inline bool dma_fence_is_container(struct dma_fence *fence)
 	return dma_fence_is_array(fence) || dma_fence_is_chain(fence);
 }
 
+#define DMA_FENCE_WARN(f, fmt, args...) \
+	do {								\
+		struct dma_fence *__ff = (f);				\
+		pr_warn("f %llu#%llu: " fmt, __ff->context, __ff->seqno,\
+			 ##args);					\
+	} while (0)
+
 #endif /* __LINUX_DMA_FENCE_H */